Amnioinfusion for meconium-stained liquor in labour

Meconium aspiration syndrome: a comprehensive review

Meconium aspiration syndrome (MAS) is a complex respiratory disease that continues to be associated with significant morbidities and mortality. The pathophysiological mechanisms of MAS include airway obstruction, local and systemic inflammation, surfactant inactivation and persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen and non-invasive respiratory support are the main therapies for many patients. The management of the patients requiring invasive mechanical ventilation could be challenging because of the combination of atelectasis and air trapping. While studies have explored various ventilatory modalities, evidence to date does not clearly support any singular modality as superior. Patient's pathophysiology, symptom severity, and clinician/unit expertise should guide the respiratory management. Early identification and concomitant management of PPHN is critically important as it contributes significantly to mortality and morbidities.

Management of Meconium-Stained Newborns in the Delivery Room

The approach to the management of meconium-stained newborns in the delivery room has been changing for over 40 years. The goal is to prevent meconium aspiration syndrome (MAS) and complications related to MAS. For decades, airway obstruction was believed to be a major component of MAS and, consequently, suction maneuvers to remove meconium from the airways were recommended to decrease the frequency and severity of MAS. Initial recommendations were based on observational studies. However, the incidence of MAS and mortality related to MAS has declined since the 1970s, mostly because of a decrease in the number of postterm deliveries. Recently updated guidelines by the American Heart Association and the Neonatal Resuscitation Program have reflected the strength of evidence supporting tracheal intubation and suctioning for nonvigorous, meconium-stained newborns. This article examines practice change since the 1970s in the delivery room management of meconium-stained newborns and evaluates evidence behind the changes.

Placental Lesions in Meconium Aspiration Syndrome

Background

Meconium aspiration syndrome (MAS) is defined by respiratory distress requiring supplemental oxygen in a meconium-stained neonate. MAS is clinically subclassified as mild, moderate, and severe according to the oxygen requirement. The aims of this study were to compare the histological findings in the placentas of MAS neonates with those of meconium-stained but non-MAS neonates and to analyze the correlation between the severity of MAS and the grade of its histological parameters.

Methods

We collected 160 singleton term placentas from neonates with meconium staining at birth from a tertiary medical center, Seoul, Republic of Korea. We reviewed hematoxylin and eosin sections of tissue samples (full-thickness placental disc, chorioamniotic membranes, and umbilical cord).

Results

Funisitis was present more frequently in MAS than in non-MAS (p < .01), of which the stage was correlated with the severity of MAS (p < .001). The histological findings consistent with maternal underperfusion and chronic deciduitis were more frequent in MAS than in non-MAS (p < .05). There was a correlation between the degree of chorionic vascular muscle necrosis and the severity of MAS (p < .05).

Conclusions

Our results suggest that fetal inflammatory response evidenced by funisitis occurs prenatally in MAS and that the stage of funisitis and of chorionic vascular muscle necrosis may be a predictive marker of the severity of MAS.

Risk factors differentiating mild/moderate from severe meconium aspiration syndrome in meconium-stained neonates

Objective

The aim of this study was to compare the risk factors associated with mild/moderate meconium aspiration syndrome (MAS) with those associated with severe in meconium-stained term neonates.

Methods

Consecutive singleton term neonates (n=671) with meconium staining at birth from all deliveries (n=14,666) in our institution from January 2006 to December 2012 were included. Both maternal and neonatal variables were examined. Among the study population, for women who underwent the trial of labor (n=644), variables associated with labor were also examined. These variables were compared between the mild/moderate MAS group, the severe MAS group, and the MAS-absent group.

Results

MAS developed in 10.6% (71/671) of neonates with meconium staining at birth. Among the neonates with MAS, 81.7% had mild MAS, 5.6% had moderate MAS, and 12.7% had severe MAS. The presence of minimal variability was significantly increased in both the mild/moderate and the severe MAS groups. The frequencies of nulliparity, fetal tachycardia, and intrapartum fever were significantly increased in the mild/moderate MAS group, but not in the severe MAS group. While a longer duration of the second stage of labor was significantly associated with mild/moderate MAS, severe MAS was associated with a shorter duration of the second stage. Notably, low mean cord pH (7.165 [6.850-7.375]) was significantly associated with mild/moderate MAS, but not with severe MAS (7.220 [7.021-7.407]) compared with the absence of MAS (7.268 [7.265-7.271]).

Conclusion

Our data suggest the development of severe MAS is not simply a linear extension of the same risk factors driving mild/moderate MAS.

Surfactant for meconium aspiration syndrome in term and late preterm infants

BACKGROUND

Surfactant replacement therapy has been proven beneficial in the prevention and treatment of neonatal respiratory distress syndrome (RDS). The deficiency of surfactant or surfactant dysfunction may contribute to respiratory failure in a broader group of disorders, including meconium aspiration syndrome (MAS).

OBJECTIVES

To evaluate the effect of surfactant administration in the treatment of late preterm and term infants with meconium aspiration syndrome.

SEARCH METHODS

We searched The Cochrane Library (Issue 4, 2006), MEDLINE and EMBASE (1985 to December 2006), previous reviews including cross-references, abstracts, conference and symposia proceedings, expert informants, and journal handsearching, without language restrictions. We contacted study authors for additional data.We ran an updated search in November 2014 and searched the following sites for ongoing or recently completed trials: www.clinicaltrials.gov; www.controlled-trials.com; and www.who.int/ictrp.

SELECTION CRITERIA

Randomised controlled trials which evaluated the effect of surfactant administration in late preterm and term infants with meconium aspiration syndrome are included in the analyses.

DATA COLLECTION AND ANALYSIS

We extracted data on clinical outcomes including mortality, treatment with extracorporeal membrane oxygenation (ECMO), pneumothorax, duration of assisted ventilation, duration of supplemental oxygen, intraventricular haemorrhage (any grade and severe IVH), and chronic lung disease. We conducted data analyses in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Four randomised controlled trials met our inclusion criteria. The meta-analysis of four trials (326 infants) showed no statistically significant effect on mortality [typical risk ratio (RR) 0.98, 95% confidence interval (CI) 0.41 to 2.39; typical risk difference (RD) -0.00, 95% CI -0.05 to 0.05]. There was no heterogeneity for this outcome (I² = 0% for both RR and RD). The risk of requiring extracorporeal membrane oxygenation was significantly reduced in a meta-analysis of two trials (n = 208); [typical RR 0.64, 95% CI 0.46 to 0.91; typical RD -0.17, 95% CI -0.30 to -0.04; number needed to treat for an additional beneficial outcome (NNTB) 6, 95% CI 3 to 25]. There was no heterogeneity for RR (1² = 0%) but moderate heterogeneity for RD (I² = 50%). One trial (n = 40) reported a statistically significant reduction in the length of hospital stay (mean difference -8 days, 95% CI -14 to -3 days; test for heterogeneity not applicable). There were no statistically significant reductions in any other outcomes studied (duration of assisted ventilation, duration of supplemental oxygen, pneumothorax, pulmonary interstitial emphysema, air leaks, chronic lung disease, need for oxygen at discharge or intraventricular haemorrhage).

AUTHORS' CONCLUSIONS

In infants with MAS, surfactant administration may reduce the severity of respiratory illness and decrease the number of infants with progressive respiratory failure requiring support with ECMO. The relative efficacy of surfactant therapy compared to, or in conjunction with, other approaches to treatment including inhaled nitric oxide, liquid ventilation, surfactant lavage and high frequency ventilation remains to be tested.

Amnioinfusion for meconium-stained liquor in labour

BACKGROUND

Amnioinfusion is thought to dilute meconium present in the amniotic fluid and so reduce the risk of meconium aspiration.

OBJECTIVES

To assess the effects of amnioinfusion for meconium-stained liquor on perinatal outcome.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (1 December 2013).

SELECTION CRITERIA

Randomised trials comparing amnioinfusion with no amnioinfusion for women in labour with moderate or thick meconium staining of the amniotic fluid.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed eligibility and trial quality, and extracted data.

MAIN RESULTS

Fourteen studies of variable quality (4435 women) are included.Subgroup analysis was performed for studies from settings with limited facilities to monitor the baby's condition during labour and intervene effectively, and settings with standard peripartum surveillance.Settings with standard peripartum surveillance: there was considerable heterogeneity for several outcomes. There was no significant reduction in the primary outcomes meconium aspiration syndrome, perinatal death or severe morbidity, and maternal death or severe morbidity. There was a reduction in caesarean sections (CSs) for fetal distress but not overall. Meconium below the vocal cords diagnosed by laryngoscopy was reduced, as was neonatal ventilation or neonatal intensive care unit admission, but there was no significant reduction in perinatal deaths or other morbidity. Planned sensitivity analysis excluding trials with greater risk of bias resulted in an absence of benefits for any of the outcomes studied.Settings with limited peripartum surveillance: three studies were included. In the amnioinfusion group there was a reduction in CS for fetal distress and overall; meconium aspiration syndrome (three studies, 1144 women; risk ratio (RR) 0.17, 95% confidence interval (CI) 0.05 to 0.52); perinatal mortality (three studies, 1151 women; RR 0.24, 95% CI 0.11 to 0.53) and neonatal ventilation or neonatal intensive care unit admission. In one of the studies, meconium below the vocal cords was reduced and, in the other, neonatal encephalopathy was reduced.

AUTHORS' CONCLUSIONS

Amnioinfusion is associated with substantive improvements in perinatal outcome only in settings where facilities for perinatal surveillance are limited. It is not clear whether the benefits are due to dilution of meconium or relief of oligohydramnios.In settings with standard peripartum surveillance, some non-substantive outcomes were improved in the initial analysis, but sensitivity analysis excluding trials with greater risk of bias eliminated these differences. Amnioinfusion is either ineffective in this setting, or its effects are masked by other strategies to optimise neonatal outcome.The trials reviewed are too small to address the possibility of rare but serious maternal adverse effects of amnioinfusion.

Delivery room management of meconium-stained infant

This article discusses the historical background, epidemiology, and pathophysiology of meconium-stained amniotic fluid and provides current concepts in delivery room management of meconium-stained neonate including the current Neonatal Resuscitation Program guidelines.

Amnioinfusion for potential or suspected umbilical cord compression in labour

BACKGROUND

Amnioinfusion aims to prevent or relieve umbilical cord compression during labour by infusing a solution into the uterine cavity.

OBJECTIVES

To assess the effects of amnioinfusion for potential or suspected umbilical cord compression on maternal and perinatal outcome .

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 October 2011).

SELECTION CRITERIA

Randomised trials of amnioinfusion compared with no amnioinfusion in women with babies at risk of umbilical cord compression in labour.

DATA COLLECTION AND ANALYSIS

The original review had one author only (Justus Hofmeyr (GJH)). For this update, two authors (GJH and T Lawrie) assessed 13 additional trial reports for eligibility and quality. We extracted data and checked for accuracy.

MAIN RESULTS

We have included 19 studies, with all but two studies having fewer than 200 participants. Transcervical amnioinfusion for potential or suspected umbilical cord compression was associated with the following reductions: caesarean section overall (13 trials, 1493 participants; average risk ratio (RR) 0.62, 95% confidence interval (CI) 0.46 to 0.83); fetal heart rate (FHR) decelerations (seven trials, 1006 participants; average RR 0.53, 95% CI 0.38 to 0.74); Apgar score less than seven at five minutes (12 trials, 1804 participants; average RR 0.47, 95% CI 0.30 to 0.72); meconium below the vocal cords (three trials, 674 participants, RR 0.53, 95% CI 0.31 to 0.92); postpartum endometritis (six trials, 767 participants; RR 0.45, 95% CI 0.25 to 0.81) and maternal hospital stay greater than three days (four trials, 1051 participants; average RR 0.45, 95% CI 0.25 to 0.78). Transabdominal amnioinfusion showed similar trends, though numbers studied were small.Mean cord umbilical artery pH was higher in the amnioinfusion group (seven trials, 855 participants; average mean difference 0.03, 95% CI 0.00 to 0.06) and there was a trend toward fewer neonates with a low cord arterial pH (less than 7.2 or as defined by trial authors) in the amnioinfusion group (eight trials, 972 participants, average RR 0.58, 95% CI 0.29 to 1.14).

AUTHORS' CONCLUSIONS

The use of amnioinfusion for potential or suspected umbilical cord compression may be of considerable benefit to mother and baby by reducing the occurrence of variable FHR decelerations, improving short-term measures of neonatal outcome, reducing maternal postpartum endometritis and lowering the use of caesarean section, although there were methodological limitations to the trials reviewed here. In addition, the trials are too small to address the possibility of rare but serious maternal adverse effects of amnioinfusion. More research is needed to confirm the findings, assess longer-term measures of fetal outcome, and to assess the impact on caesarean section rates when the diagnosis of fetal distress is more stringent. Trials should assess amnioinfusion in specific clinical situations, such as FHR decelerations, oligohydramnios or prelabour rupture of membranes.

Amnioinfusion for preterm premature rupture of membranes

BACKGROUND

Preterm premature rupture of membranes (PPROM) is a leading cause of perinatal morbidity and mortality. Amnioinfusion aims to restore amniotic fluid volume by infusing a solution into the uterine cavity.

OBJECTIVES

The objective of this review was to assess the effects of amnioinfusion for PPROM on perinatal and maternal morbidity and mortality.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2011).

SELECTION CRITERIA

Randomised trials of amnioinfusion compared to no amnioinfusion in women with PPROM.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed trials for inclusion. Two review authors independently assessed trial quality and extracted data. Data were checked for accuracy.

MAIN RESULTS

We included five trials but we only analysed data from four studies (with a total of 241 participants). One trial did not contribute any data to the review.Transcervical amnioinfusion improved fetal umbilical artery pH at delivery (mean difference 0.11; 95% confidence interval (CI) 0.08 to 0.14; one trial, 61 participants) and reduced persistent variable decelerations during labour (risk ratio (RR) 0.52; 95% CI 0.30 to 0.91; one trial, 86 participants).Transabdominal amnioinfusion was associated with a reduction in neonatal death (RR 0.30; 95% CI 0.14 to 0.66; two trials, 94 participants), neonatal sepsis (RR 0.26, 95% CI 0.11 to 0.61; one trial, 60 participants), pulmonary hypoplasia (RR 0.22; 95% CI 0.06 to 0.88; one trial, 34 participants) and puerperal sepsis (RR 0.20; 95% CI 0.05 to 0.84; one trial, 60 participants). Women in the amnioinfusion group were also less likely to deliver within seven days of membrane rupture (RR 0.18; 95% CI 0.05 to 0.70; one trial, 34 participants). These results should be treated with circumspection as the positive findings were mainly due to one trial with unclear allocation concealment.

AUTHORS' CONCLUSIONS

These results are encouraging but are limited by the sparse data and unclear methodological robustness, therefore further evidence is required before amnioinfusion for PPROM can be recommended for routine clinical practice.

Advances in the management of meconium aspiration syndrome

Meconium aspiration syndrome (MAS) is a common cause of severe respiratory distress in term infants, with an associated highly variable morbidity and mortality. MAS results from aspiration of meconium during intrauterine gasping or during the first few breaths. The pathophysiology of MAS is multifactorial and includes acute airway obstruction, surfactant dysfunction or inactivation, chemical pneumonitis with release of vasoconstrictive and inflammatory mediators, and persistent pulmonary hypertension of newborn (PPHN). This disorder can be life threatening, often complicated by respiratory failure, pulmonary air leaks, and PPHN. Approaches to the prevention of MAS have changed over time with collaboration between obstetricians and pediatricians forming the foundations for care. The use of surfactant and inhaled nitric oxide (iNO) has led to the decreased mortality and the need for extracorporeal membrane oxygenation (ECMO) use. In this paper, we review the current understanding of the pathophysiology and management of MAS.